Radiator bypass

[punes]

Simple question...how would I install a switch to manually operate the rad fan? Where would I get power from? Secondly, do I have to empty the rad coolant to change the temperature sensor that triggers the fan..I seem to have an intermintant operating switch and I have a new one to install.
Thanks

79 Fiat Spider

[spider2081]

I believe the radiator switch supplies a ground for the fan to turn on. You might first check all the conections on the ground spider on the drivers fender foward of the shock tower. The fan usually has a plug on it with a black wire and a blue wire in it. On the car side of the plug attach an additional wire (12 gauge) to the existing black wire. Switching this wire to ground should turn on the fan. The fan draws about 8 amps so the switch you use needs to be able to handle that much current. Good luck.

[punes]

Thanks, all done...I added the switch to control the fan until I replace the thermo switch. I need to order hoses and replace those at the same time, so as not to bleed the system twice. The switch I have already.
Thanks for your help.